Wash / Wipe Delay Relay Circuit Wiring

[Grizzly]

Good Morning,

It is many months, even years, since I last asked a question on here, though I have been lurking on line. My car is mechanically complete and all the wiring looms are in place.

But before I fix the dashboard permanently in place I wanted to make sure the windscreen wipers worked as access to the motor is east with no dashboard.

The problem is the intermittent selection on the wiper stalk does not work. I can follow the basic wash / wipe circuit diagram but I struggle to understand the wiper switch diagram especially the connections to the wiper delay module. The module is a Pektron Derby wiper control module (now obsolete but came from a working car which was scrapped). I opened the module box and found a printed circuit board which leaves me absolutely cold as I am not of that discipline. I do recognise the coil with a clicker switch at one end but I cannot get it to work on intermittent wiper stalk selection. The low speed selection and the high speed selection works fine. As indeed they do when the module is disconnected. I think this is because there is a live connection (Green) to the Wiper switch which activates the Low Speed (Blue /  Light Green connection) and High Speed ( Red  / Light Green connection) through the switch. But why there is another live connection (Green) to the motor I do not know and what the Brown / Light Green connection does I do not know but as it comes from the delay relay I wonder if this is the intermittent speed connection which I do not know if it is working. Looking at the circuit board with my totally inexpert eye I cannot see a timer that would activate the coil for a period  and hence the clicker.

So, how does it all work and would could be the problem? Could it be the column switch rheostat (?) and how do I test it.

I've attached the Wash / Wipe circuit diagram and a picture of the printed circuit board.

 

Thanks

 

Brian

 

 

 

 

 

 

 

 

 

 

 

I do not understand printed circuit boards

MH_Sheet 09 Wash_Wipe Circuit Diagram.pdf

[Escape]

The G wire to the motor is the ignition switched feed that allows the wipers to return to park position after you turn them off. It is fed through the switch that opens when the wiper reaches park. I think the NLG wire is to inform the delay circuit when the park position has been reached, so the timer for the next cycle can start.

Looking at the switch, you can see the delay relay is activated by grounding the LGR wire and at the same time the relay output is connected to the RLG wire for normal speed wiper operation. The delay relay is basically just a timer that (briefly) activates a relay and then resets for the next cycle. But I'm not that well versed in the circuit boards to dig much deeper either.

If normal and fast wipe works as it should, including reaching park position, and you are confident the delay relay is good, I would double check all wiring. Especially the ground connections to both the switch and delay relay.

Ooh, and don't feel bad if you're a bit overwhelmed. Wiper circuits typically appear to be black magic until you really commit yourself to figuring everything out and tracing all the connections. The Jaguar one is even worse, as it lets the wiper move in reverse to its park position if it is switched off midway! And mine isn't working as it should, so I need to have another look. 😞 

[ADF]

Dont know if it helps but my guess is the coil and clicker are the timer.  It's probably a thermal relay. Once powered, a bimetallic strip heats up cutting the connection, until it cools.

 

[Escape]

That looks more like a conventional relay coil. Judging by all the resistors and capacitors, the timer is likely an electronic circuit (charging a capacitor to a certain level for example, but happy to stand corrected).

[Grizzly]

I'mThank you both for contributing

Thank you Filip for an enlightening description of the workings of a wiper circuit and for your encouragement

I think Filip is right in suggesting that the timer is an electronic circuit (sorry Tony) and the coil and clicker are the final action of the timing circuit.

I shall bench test the delay relay as per Filip's description and let you know

 

Brian 

[Grizzly]

Well I've played around with the wiper delay relay but I am still no wiser as to how it works. In frustration as much as anything I connected the column stalk to the delay relay and connected the wires to the motor in something along the lines of the circuit diagram and switched it on. To my surprise and delight the motor responded to low speed, high speed, park and to the washer button being pressed. What did not work is the intermittent position as it should. selecting intermittent speed in any setting and the motor runs in low speed but does not drop out at all. So I have two low speed selectors and one high speed selector. Which I will live with for now. I will look for a suitable delay relay to fit somewhere in the circuit.

Trawling through the web looking for answers I found a very useful explanation of the whole wiper circuit including a Pektron delay relay on our TVR friend's forum. Link below

http://www.wedgeneering.co.uk/Wash-wipe electrics.html

 

Brian